1. Field of the Invention
The present invention relates generally to a multi-layer light emitting diode (LED) array engine. The multi-layer LED array engine can be fabricated by a very simple manufacturing process with a low manufacturing cost and a short manufacturing cycle time.
2. The Related Arts
Generally, an LED emits light in accordance with the intrinsic characteristic of the solid state semiconductor of the LED. Differing from the light emitting principle of the filament light bulb, an LED emits light when a current flows to the semiconductor PN junction, and does not need to be heated to a high temperature. As such, LEDs are also known as cold light sources. LEDs typically have the advantages including better durability, longer lifespan, lower weight, and lower power consumption. Particularly and more importantly, LEDs do not contain poisonous materials, e.g., mercury or poisonous gases. Therefore, LEDs are often used in form of a secondary assembly of LED array assembled on a printed circuit board (PCB) and have been widely employed for illumination purpose in a variety of fields, such as electronic display boards, or electronic traffic signs.
Typically, a lead frame strip is often used in assembling an LED array, in which each LED is wire bonded and molded to form an LED die. Each LED die is assembled to a lead frame pocket, and the bonded wire connects the LED die with a lead of the lead frame. The LED die and a part of the lead frame are packaged and molded to form an LED unit having external leads for electrical connection.
An LED array includes a plurality of such packaged LED units surface mounted on a pre-designed PCB or a ceramic substrate, in an array form. Such architecture is also known as a secondary level assembly of LED units. This architecture may be applied in the fields of electronic display boards or electronic traffic signs. However, according to the secondary level assembly architecture, the size of the LED products is restricted by the packaged LED unit, since the size of the packaged LED unit is much larger than the size of the die. Further, although not much, LEDs generate heat when emit light, and the only way of dissipating the generated heat in this specific architecture is from the leads to the metal lead frames. However, the leads are usually too thin to be good enough for dissipating the heat generated thereby.
According to another conventional multi-layer LED array engine, a plurality of LED dice are provided directly onto a pre-designed PCB. Specifically, the PCB is configured with circuits corresponding to the LED dice. The LED dice are electrically connected to the circuits of the PCB by bonded wires or bumps. And then, a silicon gel is used to seal the entirety of the LED array onto the PCB to form a package.
As discussed above with respect to the conventional technologies, the PCB also serves as the substrate of the multi-layer LED array. However, a PCB is usually fabricated by many complicated processes including lithographing, stamping, drilling, and plating copper in through holes. Therefore, the application of PCB as the substrate for the multi-layer LED array is not flexible, since once the PCB is prepared, it cannot be conveniently modified. As such, each multi-layer LED array must be provided with a PCB specifically designed corresponding thereto. As to the LED array, what is needed for lighting up the LED array is a loop electrically connecting thereto and supplying a current thereto. When being further provided with a heat dissipation device, the LED array can achieve a certain light emitting performance during a certain life span. Therefore, it is very much desired to provide a multi-layer LED array while simplifying the operation process and saving production cost and time thereof.